A spokesman for Ladbrokes has said the firm is "not prepared to offer long odds" on the HS2 line being subject to delays, alterations and cancellations.
The bookmaker is currently offering 4/5 that there will be delays when it comes to the opening of the service.
The government expects to complete the first phase of the high speed route from London to Birmingham by 2026, with the Manchester and Leeds extension being finished by 2033.
More top news
The operation to recover the unexploded bomb near the Houses of Parliament let to disruption in central London overnight.
Southern parts of England and Wales will see sunny skies after a frosty start.
Police said the incident in Melbourne, Australia, was terror related.